Multi-user wireless telephone having dual echo cancellers

US5999828A · kind A · utility

Assignee

• QUALCOMM Incorporated · US

Inventors

• Gilbert C. Sih · San Diego, US
• Samir Kumar Gupta · San Diego, US

Key dates

• Filing date: Mar 19, 1997
• Grant date: Dec 7, 1999
• Expiry date: Mar 19, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04B3/23
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

A method and apparatus for canceling both earseal and hybrid echo in a Wireless Local Loop telephone system is disclosed. The present invention operates within a subscriber station having a plurality of telephone inputs, one of which is a dedicated handset and at least one other input being a standard analog telephone. During a conference call between a far end speaker and two near end speakers, the far end speaker may hear an echo of his own voice due to an earseal echo generated by the dedicated handset and a hybrid echo generated by a 4-to-2 wire hybrid interface within the subscriber station. In accordance with the present invention, two distinct echo cancellers are used in the subscriber station to reduce the two types of echo. A first echo canceller is optimized to remove the earseal echo generated at the dedicated handset while a second echo canceller is optimized to remove the hybrid echo generated at the 4-to-2 wire hybrid. The two echo cancellers operate independently such that neither echo canceller need adapt its filter coefficients when a change in the echo channel characteristics occur, such as when a speaker hangs up or another speaker joins the conversation.